How Long Can I REALLY Let Car Warm Up Before Driving

["Wilks, Murray" <MWilks@xxxxxxxxxxxxxxx>]

My owner manual says NOT to run the engine a long time at idle just to
warm up the car. I think it suggests a max of 30 seconds or something
low like that. Obviously, no-one at BMW has had to wake up to a frigid
car in frosty Calgary.

Does the BMW caution against long idling (to warm up the car) arise more
from an environmental concern, or is there a valid and important
MECHANICAL reason for this?

Murray
97 318i

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